1. Field of the Invention
This invention relates to eartags for marking livestock such as cattle, sheep, pigs and other animals.
2. Prior Art
Eartags for marking livestock have been used for many years and many types have been proposed and used. Amongst the requirements for an eartag are that it can be readily fitted to the animal without injury thereto and that in use it should not be a cause of disease to the ear. It is essential that the tag should remain attached to the ear and should not pull out through engagement with snags, wire or the like. The tag should also be weatherproof so that it will not deteriorate and will remain visible.
In recent years eartags have most commonly been made of plastics material rather than metal. Such materials can readily be made weatherproof and permit of the use of various different colours for tags thereby facilitating identification. Also it is possible clearly to mark a tab of an eartag of plastics material with identification characters, e.g., letters or numbers, in a colour contrasting with the main part of the tab.
In particular identification tags of the kind described in U.S. Pat. No. 3214856 are widely used. These tags comprise a pair of separate tabs to lie flat one on each side of the part of the animal to which the tag is to be attached, one of the tabs having a single upstanding, headed spike to pass through the part of the animal to which the tag is to be attached, and the other of the tabs having a hole to receive the spike with the head of the spike entered through the hole and preventing the withdrawal of the spike from the hole, thereby of the tag to join the tabs together, said spike on the one tab and said hole in the other tab being offset from the centre of the tab towards one edge thereto to an extent such that, in use of the tag, the tabs swing round with the spike as an axis to disengage entanglements. The head of the spike is a conical tip which co-operates with the hole in the female tab to enable the eartag to be applied to the animal in a single operation. When the tag is applied to the animal, by means of a pair of pliers the spike is forced through the animal's ear and through the aperture in the female tab. Thus the hole in the ear is punched and the tag applied in a single operation.
In order to achieve this result, the female tab must have a certain amount of resilience so that the aperture can be forced over the head. On the other hand this tab and the shank have to be quite rigid in order that it is possible to punch out the hole in the animal's ear in applying the tab. This punching out of the hole in the animal's ear is effected by means of a hard shoulder constituted by the edge of the aperture and the sharp edge at the base of the conical portion of the spike. In order to punch a clean hole, the female tab and the spike must therefore be made of a material which is as hard as possible subject only to the fact that it must be possible to force the head through the aperture. If the material used for the spike and female tab is too soft, it may not be possible to punch a hole through the animal's ear. It will be appreciated that the ears of animals such as cattle and pigs are formed of fairly hard gristle. It is essential that the hole should be punched cleanly and not merely produced by a tearing action. If there is not a clean hole, it will not heal rapidly and cleanly after the tag is applied. Necrosis may set in, causing not only suffering to the animal but also ultimately loss of the eartag.
For these reasons, in the above-described prior construction, the material of the female tab and spike must be made as hard as possible suject only to the requirement that the conical head can be forced through the aperture. The dimensional tolerances are made such that the head is only just slightly larger than the aperture, just sufficient to ensure that the female tab is retained on the spike. Even so the choice of the material is very critical and, in practice, very hard nylon has to be used. It is a material which the layman would immediately describe as a rigid material. For instance the female tab cannot be bent manually.
The use of plastics material, provided the material is suitably chosen, enables the tag to be made weatherproof. In order to prevent the tags from pulling out through engagement with snags, wire, netting or fences, in the type of eartag described above, the two tabs are made relatively rotatable. It is also essential, in this prior type of eartag, that these two tabs should be quite small because, the smaller the tab, the easier it will pull clear.
Eartags made of hard nylon material, as described above, have been very extensively used for the marking of cattle, sheep, pigs and other animals. The use of a much softer material for the tab portions, such that they would flex easily and so bend or fold if caught in a snag, would be advantageous. Because the eartag is less likely to be trapped in an obstruction, larger tabs can be used, making them more readily visible. This has led to the making of an eartag of two different materials, one rigid and the other soft. British patent specification No. 1320454 is an example of such an eartag in which the female member is made of soft material and the male member of hard material. To make the male tab of soft material leads to a three-part construction as in British patent specification No. 1372769. These constructions necessarily have a stiff spike in order to enable the eartag to be applied to the animal in a single operation without prior punching of a hole.
In order to make the spike flexible, it has been proposed to form a tag with the spike as a hollow stem integral with the male tab and having a metal head, the pliers for applying the eartag having, on one jaw, a pin which, in use, extends up the bore of the spike to engage the head and stiffen the spike; one such arrangement is described in British patent specification No. 1394268 in which this pin has a pointed end and extends through the metal head. Such constructions have a number of disadvantages. The metal head has to be partly encased in plastics material with the result that there is no hard shoulder on the spike for punching a hole through the ear. Also, because of the absence of a hard shoulder, the lip for retaining the spike in the aperture of the female tab must be narrow, so making it easy to disengage the two parts of the tab. It is necessary to make the female part grip the male spike, preventing any relative movement. As a result, hairs may be trapped. This, together with tearing as a result of poor punching may cause necrosis. A further problem arises because of the pin on the plier jaw; the tag cannot be withdrawn from the pliers until the jaws are fully open and any sudden movement of the animal before then may result in the pin being broken off.